Restructure markup & markdown to prepare for multiple markup language… (#2411)

* restructure markup & markdown to prepare for multiple markup languages support

* adjust some functions between markdown and markup

* fix tests

* improve the comments

1 files changed, 28 insertions, 546 deletions

diff --git a/modules/markdown/markdown.go b/modules/markdown/markdown.go
index ed673f2056..6cf2d9eaa1 100644
--- a/modules/markdown/markdown.go
+++ b/modules/markdown/markdown.go
@@ -6,107 +6,14 @@ package markdown
 
 import (
 	"bytes"
-	"fmt"
-	"io"
-	"net/url"
-	"path"
-	"path/filepath"
-	"regexp"
 	"strings"
 
-	"code.gitea.io/gitea/modules/base"
-	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/markup"
 	"code.gitea.io/gitea/modules/setting"
 
-	"github.com/Unknwon/com"
 	"github.com/russross/blackfriday"
-	"golang.org/x/net/html"
 )
 
-// Issue name styles
-const (
-	IssueNameStyleNumeric      = "numeric"
-	IssueNameStyleAlphanumeric = "alphanumeric"
-)
-
-// IsMarkdownFile reports whether name looks like a Markdown file
-// based on its extension.
-func IsMarkdownFile(name string) bool {
-	extension := strings.ToLower(filepath.Ext(name))
-	for _, ext := range setting.Markdown.FileExtensions {
-		if strings.ToLower(ext) == extension {
-			return true
-		}
-	}
-	return false
-}
-
-var (
-	// NOTE: All below regex matching do not perform any extra validation.
-	// Thus a link is produced even if the user does not exist, the issue does not exist, the commit does not exist, etc.
-	// While fast, this is also incorrect and lead to false positives.
-
-	// MentionPattern matches string that mentions someone, e.g. @Unknwon
-	MentionPattern = regexp.MustCompile(`(\s|^|\W)@[0-9a-zA-Z-_\.]+`)
-
-	// IssueNumericPattern matches string that references to a numeric issue, e.g. #1287
-	IssueNumericPattern = regexp.MustCompile(`( |^|\()#[0-9]+\b`)
-	// IssueAlphanumericPattern matches string that references to an alphanumeric issue, e.g. ABC-1234
-	IssueAlphanumericPattern = regexp.MustCompile(`( |^|\()[A-Z]{1,10}-[1-9][0-9]*\b`)
-	// CrossReferenceIssueNumericPattern matches string that references a numeric issue in a different repository
-	// e.g. gogits/gogs#12345
-	CrossReferenceIssueNumericPattern = regexp.MustCompile(`( |^)[0-9a-zA-Z]+/[0-9a-zA-Z]+#[0-9]+\b`)
-
-	// Sha1CurrentPattern matches string that represents a commit SHA, e.g. d8a994ef243349f321568f9e36d5c3f444b99cae
-	// Although SHA1 hashes are 40 chars long, the regex matches the hash from 7 to 40 chars in length
-	// so that abbreviated hash links can be used as well. This matches git and github useability.
-	Sha1CurrentPattern = regexp.MustCompile(`(?:^|\s|\()([0-9a-f]{7,40})\b`)
-
-	// ShortLinkPattern matches short but difficult to parse [[name|link|arg=test]] syntax
-	ShortLinkPattern = regexp.MustCompile(`(\[\[.*?\]\]\w*)`)
-
-	// AnySHA1Pattern allows to split url containing SHA into parts
-	AnySHA1Pattern = regexp.MustCompile(`(http\S*)://(\S+)/(\S+)/(\S+)/(\S+)/([0-9a-f]{40})(?:/?([^#\s]+)?(?:#(\S+))?)?`)
-
-	validLinksPattern = regexp.MustCompile(`^[a-z][\w-]+://`)
-)
-
-// regexp for full links to issues/pulls
-var issueFullPattern *regexp.Regexp
-
-// InitMarkdown initialize regexps for markdown parsing
-func InitMarkdown() {
-	getIssueFullPattern()
-}
-
-func getIssueFullPattern() *regexp.Regexp {
-	if issueFullPattern == nil {
-		appURL := setting.AppURL
-		if len(appURL) > 0 && appURL[len(appURL)-1] != '/' {
-			appURL += "/"
-		}
-		issueFullPattern = regexp.MustCompile(appURL +
-			`\w+/\w+/(?:issues|pulls)/((?:\w{1,10}-)?[1-9][0-9]*)([\?|#]\S+.(\S+)?)?\b`)
-	}
-	return issueFullPattern
-}
-
-// isLink reports whether link fits valid format.
-func isLink(link []byte) bool {
-	return validLinksPattern.Match(link)
-}
-
-// FindAllMentions matches mention patterns in given content
-// and returns a list of found user names without @ prefix.
-func FindAllMentions(content string) []string {
-	mentions := MentionPattern.FindAllString(content, -1)
-	for i := range mentions {
-		mentions[i] = mentions[i][strings.Index(mentions[i], "@")+1:] // Strip @ character
-	}
-	return mentions
-}
-
 // Renderer is a extended version of underlying render object.
 type Renderer struct {
 	blackfriday.Renderer
@@ -116,13 +23,13 @@ type Renderer struct {
 
 // Link defines how formal links should be processed to produce corresponding HTML elements.
 func (r *Renderer) Link(out *bytes.Buffer, link []byte, title []byte, content []byte) {
-	if len(link) > 0 && !isLink(link) {
+	if len(link) > 0 && !markup.IsLink(link) {
 		if link[0] != '#' {
 			lnk := string(link)
 			if r.isWikiMarkdown {
-				lnk = URLJoin("wiki", lnk)
+				lnk = markup.URLJoin("wiki", lnk)
 			}
-			mLink := URLJoin(r.urlPrefix, lnk)
+			mLink := markup.URLJoin(r.urlPrefix, lnk)
 			link = []byte(mLink)
 		}
 	}
@@ -190,11 +97,11 @@ var (
 func (r *Renderer) Image(out *bytes.Buffer, link []byte, title []byte, alt []byte) {
 	prefix := r.urlPrefix
 	if r.isWikiMarkdown {
-		prefix = URLJoin(prefix, "wiki", "src")
+		prefix = markup.URLJoin(prefix, "wiki", "src")
 	}
 	prefix = strings.Replace(prefix, "/src/", "/raw/", 1)
 	if len(link) > 0 {
-		if isLink(link) {
+		if markup.IsLink(link) {
 			// External link with .svg suffix usually means CI status.
 			// TODO: define a keyword to allow non-svg images render as external link.
 			if bytes.HasSuffix(link, svgSuffix) || bytes.Contains(link, svgSuffixWithMark) {
@@ -203,7 +110,7 @@ func (r *Renderer) Image(out *bytes.Buffer, link []byte, title []byte, alt []byt
 			}
 		} else {
 			lnk := string(link)
-			lnk = URLJoin(prefix, lnk)
+			lnk = markup.URLJoin(prefix, lnk)
 			lnk = strings.Replace(lnk, " ", "+", -1)
 			link = []byte(lnk)
 		}
@@ -216,351 +123,6 @@ func (r *Renderer) Image(out *bytes.Buffer, link []byte, title []byte, alt []byt
 	out.WriteString("</a>")
 }
 
-// cutoutVerbosePrefix cutouts URL prefix including sub-path to
-// return a clean unified string of request URL path.
-func cutoutVerbosePrefix(prefix string) string {
-	if len(prefix) == 0 || prefix[0] != '/' {
-		return prefix
-	}
-	count := 0
-	for i := 0; i < len(prefix); i++ {
-		if prefix[i] == '/' {
-			count++
-		}
-		if count >= 3+setting.AppSubURLDepth {
-			return prefix[:i]
-		}
-	}
-	return prefix
-}
-
-// URLJoin joins url components, like path.Join, but preserving contents
-func URLJoin(base string, elems ...string) string {
-	u, err := url.Parse(base)
-	if err != nil {
-		log.Error(4, "URLJoin: Invalid base URL %s", base)
-		return ""
-	}
-	joinArgs := make([]string, 0, len(elems)+1)
-	joinArgs = append(joinArgs, u.Path)
-	joinArgs = append(joinArgs, elems...)
-	u.Path = path.Join(joinArgs...)
-	return u.String()
-}
-
-// RenderIssueIndexPattern renders issue indexes to corresponding links.
-func RenderIssueIndexPattern(rawBytes []byte, urlPrefix string, metas map[string]string) []byte {
-	urlPrefix = cutoutVerbosePrefix(urlPrefix)
-
-	pattern := IssueNumericPattern
-	if metas["style"] == IssueNameStyleAlphanumeric {
-		pattern = IssueAlphanumericPattern
-	}
-
-	ms := pattern.FindAll(rawBytes, -1)
-	for _, m := range ms {
-		if m[0] == ' ' || m[0] == '(' {
-			m = m[1:] // ignore leading space or opening parentheses
-		}
-		var link string
-		if metas == nil {
-			link = fmt.Sprintf(`<a href="%s">%s</a>`, URLJoin(urlPrefix, "issues", string(m[1:])), m)
-		} else {
-			// Support for external issue tracker
-			if metas["style"] == IssueNameStyleAlphanumeric {
-				metas["index"] = string(m)
-			} else {
-				metas["index"] = string(m[1:])
-			}
-			link = fmt.Sprintf(`<a href="%s">%s</a>`, com.Expand(metas["format"], metas), m)
-		}
-		rawBytes = bytes.Replace(rawBytes, m, []byte(link), 1)
-	}
-	return rawBytes
-}
-
-// IsSameDomain checks if given url string has the same hostname as current Gitea instance
-func IsSameDomain(s string) bool {
-	if strings.HasPrefix(s, "/") {
-		return true
-	}
-	if uapp, err := url.Parse(setting.AppURL); err == nil {
-		if u, err := url.Parse(s); err == nil {
-			return u.Host == uapp.Host
-		}
-		return false
-	}
-	return false
-}
-
-// renderFullSha1Pattern renders SHA containing URLs
-func renderFullSha1Pattern(rawBytes []byte, urlPrefix string) []byte {
-	ms := AnySHA1Pattern.FindAllSubmatch(rawBytes, -1)
-	for _, m := range ms {
-		all := m[0]
-		protocol := string(m[1])
-		paths := string(m[2])
-		path := protocol + "://" + paths
-		author := string(m[3])
-		repoName := string(m[4])
-		path = URLJoin(path, author, repoName)
-		ltype := "src"
-		itemType := m[5]
-		if IsSameDomain(paths) {
-			ltype = string(itemType)
-		} else if string(itemType) == "commit" {
-			ltype = "commit"
-		}
-		sha := m[6]
-		var subtree string
-		if len(m) > 7 && len(m[7]) > 0 {
-			subtree = string(m[7])
-		}
-		var line []byte
-		if len(m) > 8 && len(m[8]) > 0 {
-			line = m[8]
-		}
-		urlSuffix := ""
-		text := base.ShortSha(string(sha))
-		if subtree != "" {
-			urlSuffix = "/" + subtree
-			text += urlSuffix
-		}
-		if line != nil {
-			value := string(line)
-			urlSuffix += "#"
-			urlSuffix += value
-			text += " ("
-			text += value
-			text += ")"
-		}
-		rawBytes = bytes.Replace(rawBytes, all, []byte(fmt.Sprintf(
-			`<a href="%s">%s</a>`, URLJoin(path, ltype, string(sha))+urlSuffix, text)), -1)
-	}
-	return rawBytes
-}
-
-// RenderFullIssuePattern renders issues-like URLs
-func RenderFullIssuePattern(rawBytes []byte) []byte {
-	ms := getIssueFullPattern().FindAllSubmatch(rawBytes, -1)
-	for _, m := range ms {
-		all := m[0]
-		id := string(m[1])
-		text := "#" + id
-		// TODO if m[2] is not nil, then link is to a comment,
-		// and we should indicate that in the text somehow
-		rawBytes = bytes.Replace(rawBytes, all, []byte(fmt.Sprintf(
-			`<a href="%s">%s</a>`, string(all), text)), -1)
-	}
-	return rawBytes
-}
-
-func firstIndexOfByte(sl []byte, target byte) int {
-	for i := 0; i < len(sl); i++ {
-		if sl[i] == target {
-			return i
-		}
-	}
-	return -1
-}
-
-func lastIndexOfByte(sl []byte, target byte) int {
-	for i := len(sl) - 1; i >= 0; i-- {
-		if sl[i] == target {
-			return i
-		}
-	}
-	return -1
-}
-
-// RenderShortLinks processes [[syntax]]
-//
-// noLink flag disables making link tags when set to true
-// so this function just replaces the whole [[...]] with the content text
-//
-// isWikiMarkdown is a flag to choose linking url prefix
-func RenderShortLinks(rawBytes []byte, urlPrefix string, noLink bool, isWikiMarkdown bool) []byte {
-	ms := ShortLinkPattern.FindAll(rawBytes, -1)
-	for _, m := range ms {
-		orig := bytes.TrimSpace(m)
-		m = orig[2:]
-		tailPos := lastIndexOfByte(m, ']') + 1
-		tail := []byte{}
-		if tailPos < len(m) {
-			tail = m[tailPos:]
-			m = m[:tailPos-1]
-		}
-		m = m[:len(m)-2]
-		props := map[string]string{}
-
-		// MediaWiki uses [[link|text]], while GitHub uses [[text|link]]
-		// It makes page handling terrible, but we prefer GitHub syntax
-		// And fall back to MediaWiki only when it is obvious from the look
-		// Of text and link contents
-		sl := bytes.Split(m, []byte("|"))
-		for _, v := range sl {
-			switch bytes.Count(v, []byte("=")) {
-
-			// Piped args without = sign, these are mandatory arguments
-			case 0:
-				{
-					sv := string(v)
-					if props["name"] == "" {
-						if isLink(v) {
-							// If we clearly see it is a link, we save it so
-
-							// But first we need to ensure, that if both mandatory args provided
-							// look like links, we stick to GitHub syntax
-							if props["link"] != "" {
-								props["name"] = props["link"]
-							}
-
-							props["link"] = strings.TrimSpace(sv)
-						} else {
-							props["name"] = sv
-						}
-					} else {
-						props["link"] = strings.TrimSpace(sv)
-					}
-				}
-
-			// Piped args with = sign, these are optional arguments
-			case 1:
-				{
-					sep := firstIndexOfByte(v, '=')
-					key, val := string(v[:sep]), html.UnescapeString(string(v[sep+1:]))
-					lastCharIndex := len(val) - 1
-					if (val[0] == '"' || val[0] == '\'') && (val[lastCharIndex] == '"' || val[lastCharIndex] == '\'') {
-						val = val[1:lastCharIndex]
-					}
-					props[key] = val
-				}
-			}
-		}
-
-		var name string
-		var link string
-		if props["link"] != "" {
-			link = props["link"]
-		} else if props["name"] != "" {
-			link = props["name"]
-		}
-		if props["title"] != "" {
-			name = props["title"]
-		} else if props["name"] != "" {
-			name = props["name"]
-		} else {
-			name = link
-		}
-
-		name += string(tail)
-		image := false
-		ext := filepath.Ext(string(link))
-		if ext != "" {
-			switch ext {
-			case ".jpg", ".jpeg", ".png", ".tif", ".tiff", ".webp", ".gif", ".bmp", ".ico", ".svg":
-				{
-					image = true
-				}
-			}
-		}
-		absoluteLink := isLink([]byte(link))
-		if !absoluteLink {
-			link = strings.Replace(link, " ", "+", -1)
-		}
-		if image {
-			if !absoluteLink {
-				if IsSameDomain(urlPrefix) {
-					urlPrefix = strings.Replace(urlPrefix, "/src/", "/raw/", 1)
-				}
-				if isWikiMarkdown {
-					link = URLJoin("wiki", "raw", link)
-				}
-				link = URLJoin(urlPrefix, link)
-			}
-			title := props["title"]
-			if title == "" {
-				title = props["alt"]
-			}
-			if title == "" {
-				title = path.Base(string(name))
-			}
-			alt := props["alt"]
-			if alt == "" {
-				alt = name
-			}
-			if alt != "" {
-				alt = `alt="` + alt + `"`
-			}
-			name = fmt.Sprintf(`<img src="%s" %s title="%s" />`, link, alt, title)
-		} else if !absoluteLink {
-			if isWikiMarkdown {
-				link = URLJoin("wiki", link)
-			}
-			link = URLJoin(urlPrefix, link)
-		}
-		if noLink {
-			rawBytes = bytes.Replace(rawBytes, orig, []byte(name), -1)
-		} else {
-			rawBytes = bytes.Replace(rawBytes, orig,
-				[]byte(fmt.Sprintf(`<a href="%s">%s</a>`, link, name)), -1)
-		}
-	}
-	return rawBytes
-}
-
-// RenderCrossReferenceIssueIndexPattern renders issue indexes from other repositories to corresponding links.
-func RenderCrossReferenceIssueIndexPattern(rawBytes []byte, urlPrefix string, metas map[string]string) []byte {
-	ms := CrossReferenceIssueNumericPattern.FindAll(rawBytes, -1)
-	for _, m := range ms {
-		if m[0] == ' ' || m[0] == '(' {
-			m = m[1:] // ignore leading space or opening parentheses
-		}
-
-		repo := string(bytes.Split(m, []byte("#"))[0])
-		issue := string(bytes.Split(m, []byte("#"))[1])
-
-		link := fmt.Sprintf(`<a href="%s">%s</a>`, URLJoin(setting.AppURL, repo, "issues", issue), m)
-		rawBytes = bytes.Replace(rawBytes, m, []byte(link), 1)
-	}
-	return rawBytes
-}
-
-// renderSha1CurrentPattern renders SHA1 strings to corresponding links that assumes in the same repository.
-func renderSha1CurrentPattern(rawBytes []byte, urlPrefix string) []byte {
-	ms := Sha1CurrentPattern.FindAllSubmatch(rawBytes, -1)
-	for _, m := range ms {
-		hash := m[1]
-		// The regex does not lie, it matches the hash pattern.
-		// However, a regex cannot know if a hash actually exists or not.
-		// We could assume that a SHA1 hash should probably contain alphas AND numerics
-		// but that is not always the case.
-		// Although unlikely, deadbeef and 1234567 are valid short forms of SHA1 hash
-		// as used by git and github for linking and thus we have to do similar.
-		rawBytes = bytes.Replace(rawBytes, hash, []byte(fmt.Sprintf(
-			`<a href="%s">%s</a>`, URLJoin(urlPrefix, "commit", string(hash)), base.ShortSha(string(hash)))), -1)
-	}
-	return rawBytes
-}
-
-// RenderSpecialLink renders mentions, indexes and SHA1 strings to corresponding links.
-func RenderSpecialLink(rawBytes []byte, urlPrefix string, metas map[string]string, isWikiMarkdown bool) []byte {
-	ms := MentionPattern.FindAll(rawBytes, -1)
-	for _, m := range ms {
-		m = m[bytes.Index(m, []byte("@")):]
-		rawBytes = bytes.Replace(rawBytes, m,
-			[]byte(fmt.Sprintf(`<a href="%s">%s</a>`, URLJoin(setting.AppURL, string(m[1:])), m)), -1)
-	}
-
-	rawBytes = RenderFullIssuePattern(rawBytes)
-	rawBytes = RenderShortLinks(rawBytes, urlPrefix, false, isWikiMarkdown)
-	rawBytes = RenderIssueIndexPattern(rawBytes, urlPrefix, metas)
-	rawBytes = RenderCrossReferenceIssueIndexPattern(rawBytes, urlPrefix, metas)
-	rawBytes = renderFullSha1Pattern(rawBytes, urlPrefix)
-	rawBytes = renderSha1CurrentPattern(rawBytes, urlPrefix)
-	return rawBytes
-}
-
 // RenderRaw renders Markdown to HTML without handling special links.
 func RenderRaw(body []byte, urlPrefix string, wikiMarkdown bool) []byte {
 	htmlFlags := 0
@@ -589,107 +151,6 @@ func RenderRaw(body []byte, urlPrefix string, wikiMarkdown bool) []byte {
 }
 
 var (
-	leftAngleBracket  = []byte("</")
-	rightAngleBracket = []byte(">")
-)
-
-var noEndTags = []string{"img", "input", "br", "hr"}
-
-// PostProcess treats different types of HTML differently,
-// and only renders special links for plain text blocks.
-func PostProcess(rawHTML []byte, urlPrefix string, metas map[string]string, isWikiMarkdown bool) []byte {
-	startTags := make([]string, 0, 5)
-	var buf bytes.Buffer
-	tokenizer := html.NewTokenizer(bytes.NewReader(rawHTML))
-
-OUTER_LOOP:
-	for html.ErrorToken != tokenizer.Next() {
-		token := tokenizer.Token()
-		switch token.Type {
-		case html.TextToken:
-			buf.Write(RenderSpecialLink([]byte(token.String()), urlPrefix, metas, isWikiMarkdown))
-
-		case html.StartTagToken:
-			buf.WriteString(token.String())
-			tagName := token.Data
-			// If this is an excluded tag, we skip processing all output until a close tag is encountered.
-			if strings.EqualFold("a", tagName) || strings.EqualFold("code", tagName) || strings.EqualFold("pre", tagName) {
-				stackNum := 1
-				for html.ErrorToken != tokenizer.Next() {
-					token = tokenizer.Token()
-
-					// Copy the token to the output verbatim
-					buf.Write(RenderShortLinks([]byte(token.String()), urlPrefix, true, isWikiMarkdown))
-
-					if token.Type == html.StartTagToken && !com.IsSliceContainsStr(noEndTags, token.Data) {
-						stackNum++
-					}
-
-					// If this is the close tag to the outer-most, we are done
-					if token.Type == html.EndTagToken {
-						stackNum--
-
-						if stackNum <= 0 && strings.EqualFold(tagName, token.Data) {
-							break
-						}
-					}
-				}
-				continue OUTER_LOOP
-			}
-
-			if !com.IsSliceContainsStr(noEndTags, tagName) {
-				startTags = append(startTags, tagName)
-			}
-
-		case html.EndTagToken:
-			if len(startTags) == 0 {
-				buf.WriteString(token.String())
-				break
-			}
-
-			buf.Write(leftAngleBracket)
-			buf.WriteString(startTags[len(startTags)-1])
-			buf.Write(rightAngleBracket)
-			startTags = startTags[:len(startTags)-1]
-		default:
-			buf.WriteString(token.String())
-		}
-	}
-
-	if io.EOF == tokenizer.Err() {
-		return buf.Bytes()
-	}
-
-	// If we are not at the end of the input, then some other parsing error has occurred,
-	// so return the input verbatim.
-	return rawHTML
-}
-
-// Render renders Markdown to HTML with all specific handling stuff.
-func render(rawBytes []byte, urlPrefix string, metas map[string]string, isWikiMarkdown bool) []byte {
-	urlPrefix = strings.Replace(urlPrefix, " ", "+", -1)
-	result := RenderRaw(rawBytes, urlPrefix, isWikiMarkdown)
-	result = PostProcess(result, urlPrefix, metas, isWikiMarkdown)
-	result = SanitizeBytes(result)
-	return result
-}
-
-// Render renders Markdown to HTML with all specific handling stuff.
-func Render(rawBytes []byte, urlPrefix string, metas map[string]string) []byte {
-	return render(rawBytes, urlPrefix, metas, false)
-}
-
-// RenderString renders Markdown to HTML with special links and returns string type.
-func RenderString(raw, urlPrefix string, metas map[string]string) string {
-	return string(render([]byte(raw), urlPrefix, metas, false))
-}
-
-// RenderWiki renders markdown wiki page to HTML and return HTML string
-func RenderWiki(rawBytes []byte, urlPrefix string, metas map[string]string) string {
-	return string(render(rawBytes, urlPrefix, metas, true))
-}
-
-var (
 	// MarkupName describes markup's name
 	MarkupName = "markdown"
 )
@@ -714,5 +175,26 @@ func (Parser) Extensions() []string {
 
 // Render implements markup.Parser
 func (Parser) Render(rawBytes []byte, urlPrefix string, metas map[string]string, isWiki bool) []byte {
-	return render(rawBytes, urlPrefix, metas, isWiki)
+	return RenderRaw(rawBytes, urlPrefix, isWiki)
+}
+
+// Render renders Markdown to HTML with all specific handling stuff.
+func Render(rawBytes []byte, urlPrefix string, metas map[string]string) []byte {
+	return markup.Render("a.md", rawBytes, urlPrefix, metas)
+}
+
+// RenderString renders Markdown to HTML with special links and returns string type.
+func RenderString(raw, urlPrefix string, metas map[string]string) string {
+	return markup.RenderString("a.md", raw, urlPrefix, metas)
+}
+
+// RenderWiki renders markdown wiki page to HTML and return HTML string
+func RenderWiki(rawBytes []byte, urlPrefix string, metas map[string]string) string {
+	return markup.RenderWiki("a.md", rawBytes, urlPrefix, metas)
+}
+
+// IsMarkdownFile reports whether name looks like a Markdown file
+// based on its extension.
+func IsMarkdownFile(name string) bool {
+	return markup.IsMarkupFile(name, MarkupName)
 }